#include<vector>
using namespace std;
 struct ListNode {
     int val;
     ListNode *next;
     ListNode(int x) : val(x), next(NULL) {}
 };

class Solution {
public:
    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        ListNode*dummy = new ListNode(0);
        ListNode *curr = dummy;
        while (l1 != NULL && l2!=NULL)
        {
            if(l1->val<l2->val)
            {
                curr->next = l1;
                l1 = l1->next;
            }
            else
            {
                curr->next = l2;
                l2 = l2->next;
            }
            curr = curr->next;
        }
        if(l1!=NULL)
            curr->next = l1;
        else
            curr->next = l2;
        
        return dummy->next;

    }
};